(Gr. haloms, “nimbus”). A circle or disc of light with which the head of Christ, the Virgin Mary, or a saint is surrounded in Christian art. This usage was taken over from religious symbolism within Hellenism and the Roman Empire, wherein gods and some emperors were represented with halos around their bodies or heads. Since the third century there has been a gradual development of usage within Christendom. At first it was deemed proper only to use the halo, whose usual color was blue, for Christ, but from the time of Leo I it was extended to include the Virgin and the saints. During the Middle Ages several types were in currency, but the color now was usually yellow or gold. A plain, round halo was used for angels and saints; a round one with a suitable distinguishing characteristic (e.g., a cross or monogram) for Christ; and a rectangular one for living dignitaries—e.g., that of Gregory the Great in the monastery of Clivus Scauri at Rome. Within contemporary Catholicism the halo is used only for the saints and those of the “blessed” who are venerated.